Potentiometer terminal



y 30, 1967 P. v. DE LUCA ETAL 3,323,094

POTENTIOMETER TERMINAL Filed July 29, 1964 F K3. 4B

INVENTORS PAULVDQ LUCA BY HARVEY 5. savrr MM Kw ATTORNEY United StatesPatent 3,323,094 POTENTIOMETER TERMINAL Paul V. De Luca, JacksonHeights, and Harvey E. Senft, White Plains, N.Y., assignors to MarkiteCorporation, New York, N.Y.

Filed July 29, 1964, Ser. No. 385,847 13 Claims. (Cl. 338162) Inextremely small potentiometers, which are commonly used where weight andsize are factors, the internal area available for the manipulation ofassembly tools is quite limited. Accordingly, past methods of providingthe aforementioned external-internal conductive paths have been awkwardand tedious, representing a long standing problem in the industry.

There also exists particularly stringent requirements for ruggedness,accuracy and reliability for potentiometers which are incorporated inspace vehicles, computers and other demanding applications. Adding tothe problem is the fact that the components involved are both delicateand costly.

The terminals must withstand torsional and tensile loads during andafter assembly and must retain electrical continuity over a wide rangeof temperatures. The difficulties inherent in assembling components ofthis nature make it imperative to improve the techniques whereeverpossible.

The present invention is directed towards this end by providing improvedconnecting means which may be employed in high precision potentiometers.By way of example, there will be disclosed hereinafter the employment ofthe terminal assembly, comprising the present invention, in apotentiometer. The terminal passes through the housing wall so that, inone embodiment, the internal end of the terminal which is split orbifurcated will be at right angles to and will straddle a comolded,electrically conductive stud in electrical connection with the resistiveelement of the potentiometer. Alternatively, the terminal may be formedwithout the bifurcating slot and the conductive stud would, in thiscase, be a wire secured to the resistive element of the potentiometer.In either embodiment the terminal is provided with a longitudinal boreand a transverse, annular groove axially displaced from the bored end ofthe terminal. One edge of the annular groove and the bored end of thestud define that portion of the terminal which subsequently experiencesdeformation. A flanged head is also provided which, in cooperation withone confronting edge of the annular groove, defines an axial terminalonly slightly greater than the wall thickness through which it passes.

The terminal body is then crimped at a point between the annular grooveand the bored end of the terminal. The body of the terminal is therebymade larger than the hole in the wall through which the terminal wasoriginally inserted thus preventing longitudinal movement of theterminal. Solder is then melted to flow in and fill the remaining gapbetween the stud and the inside surface of the terminal bifurcation. Inplace of solder, electrical connection may be made by welding theterminal and stud after crimping. A suitable bonding agent, such asepoxy resin, may then be applied to the internal and external ends,respectively, of the terminal to further mechanically secure it to thepotentiometer housing wall.

It is therefore an object of this invention to provide an improvedterminal assembly suitable for a small precision electrical device.

It is another object to provide improved connection means betweeninternal taps and external terminals of a potentiometer.

An additional object is to provide an improved terminal and terminalconnecting means consistent in size with small potentiometers and yetadaptable to assembly by conventional techniques.

Still another object is to provide an improved terminal and terminalconnection means of small size that are convenient to assemble at a lowcost.

A further object is to provide a small but rugged potentiometer terminalthat may be assembled by inexpensive techniques.

These and other features, objects and advantages of the invention will,in part, be pointed out with particularity and will, in part, becomeobvious from the following more detailed description of the invention,taken in conjunction with the accompanying drawing, which forms anintegral part thereof.

In the various figures of the drawing, like reference charactersdesignate like parts.

In the drawing:

FIG. 1 is an end elevation of a rotary potentiometer assemblyincorporating the present invention;

FIG. 2 is a cross sectional view taken along line 2-2 of FIG. 1;

FIG. 3A is an enlarged detail view of an external terminal embodying theconcept of the present invention, the terminal being shown in relationto a potentiometer stud prior to crimping;

FIG. 3B is a transverse end elevation view taken along line 3B3B of FIG.3A;

FIG. 4A is an enlarged view similar to FIG. 3A but subsequent tocrimping and rotated degrees about the longitudinal terminal axis. Thedeformed portion of the assembled terminal, as well as a portion of thehousing and the stud, are shown; and

' FIG. 4B is a transverse end elevation view taken along line 4B4B ofFIG. 4A.

In FIG. 1 and FIG. 2, there is shown a compact, precision type rotarypotentiometer 10 employing radial terminals 12a, 12b, 12c and 12d. Shaft14 is coaxial and concentric with cylindrical housing portions 16 and 18and is suitably journaled therein by means of bearings 20 and 22,respectively. Servo flange 24, in combination with a dog type clamp Cand screws S, represent a conventional means for mounting potentiometer10 to panel P. A disc shaped, insulating base member 26 is sandwichedbetween and secured concentrically with housing portions 16 and 18 bymeans of screws 28. As may be seen in FIG. 2, the heads of screws arecontained in recesses formed in housing portion 16 and the shanks of thescrews pass through clearance holes 30 formed in base member 26. Theends of screws 28 are engaged "in threaded apertures 32 formed inhousing portion 18.

FIG. 1 also illustrates the shape and position of a comolded, conductiveresistive track 34, which is coaxial and concentric with shaft 14.Conductive paths 36a and 36b, are aifixed to base member 26 and contactarcuate track 34 proximate the ends thereof. The short, remaining are 38is filled with an insulator plastic to electrically isolate the trackends from each other and to permit continuous 360-degree rotation of thewiper contacts.

Brush block 40 is rigidly secured to shaft 14 by means of set screw 42.The bush block is comprised of an inner sleeve 44, an intermediate,insulating sleeve 46 and an outer, conductive sleeve 48. A wiperassembly comprising arm 50 and precious metal contact 52 is secured tothe brush block for rotation therewith and is in sliding contact withtrack 34. Thus, rotation of shaft 14 will cause rotation of the brushblock and the wiper assembly causing a variance in the output voltageof'the potentiometer corresponding to the angular displacement of theshaft as measured between one terminal and the Wiper. Additionally,there is integrally formed on the brush block a hub portion 54,concentric and rotatable with shaft 14 and in electrical contact withsleeve 48. A hairspring wiper 56, secured to a stud which will be fullydescribed hereinafter, is located such that its spaced legs ride onrotating V-shaped outer surface of hub 54.

Studs 58a, 58b, 58c and 58d are molded into base member 26 and extendfrom the face thereof opposite track 34. Studs 58a and 58b are inelectrical contact with conductive paths 36a and 36b and with terminals12a and 12b, respectively. Studs 58c may be positioned in the insulatorplastic between studs 58a and 58b in electrical contact with terminal12c and stud 58d, by way of example, may be a center tap situated at themidpoint of the resistive trackin electrical contact with terminal 12d.In the embodiment illustrated, hairspring wiper 56 is soldered to stud580.

As shown in FIG. 3A and FIG. 3B, terminal 12 is a multidiameter rodhaving one end portion 60 bifurcated by slot 62. Axial bore 64, which isof the same size as or is slightly larger in diameter than slot 62,extends inwardly from end 60 past a reduced diameter, thin walledportion 66 and terminates in the area of knurled body portion 68. Inorderto simplify the manufacturing techniques, the terminal is furtherprovided with an additional reduced diameter portion 70, adjacent bodyportion 68, as Well as an enlarged diameter 72 and a shank 74. Reduceddiameter portion 70 is not essential; it is convenient to machine itthat Way in order to avoid a fillet between the shank of the terminaland the flange.

Terminal 12 is secured into a suitably sized radial opening 25 in theannular, flange portion 26a of base member 26 which, in this embodiment,forms a part of the housing wall. Body portion 68 is knurled to providea snug fit with radial opening 25 when the enlarged diameter 72 isseated on the outside surface of flange 2611. When using a relativelybrittle phenolic plastic for the housing, the CD. of the knurling andthe ID. of the radial opening are sized for a 0.001" to 0.003"clearance. Where a softer material forms the Wall it is practical topressfit the terminal in place. Once installed in a straddlingrelationship about one of the studs, end portion 60 is crimped so thatbore 64 is collapsed around the stud in the area of slot 62. At the sametime and by means of the aforementioned crimping action, wall 66a ofannular groove 66 is also distorted into a noncircular shape. Theenlarged surface of wall 66a then abuts the inner face of flange 2611.It should be noted that the thin walled, annular groove 66 prevents thetransmission of the crimping deformation from end portion 60 to bodyportion 68. Reduced diameter portion 66 is weak in comparison to theother sections.

The result of the crimping is best illustrated in FIG. 4A and FIG. 4Bwherein it will be seen that in addition to being closed around theconductive stud, end portion 60 and particularly the portion thereofproximate groove 66 has assumed a somewhat oval shape. That is, aftercrimping, end portion 60 and wall 66a have a major diameter D and aminor diameter d. The major diameter is larger than the hole in the wallof the potentiometer housing and the terminal is captured between Wall66a of annular groove 66 and flange 72. It should be noted that FIG. 4Ais rotated 90 degrees about the longitudinal axis of the terminal withrespect to FIG. 3A.

In a preferred embodiment, an epoxy resin is applied to the insidesurface of flange 26a in the vicinity of the terminal. By capillaryaction, the epoxy flows through the channels formed by the knurling ofthe body portion 68 and out between enlarged diameter 72 and the housingWall to form a bead thereabout. The use of epoxy helps to prevent bothwithdrawal of terminal 12 through flange 26a and twisting of theterminal.

Referring once again to FIG. 3A, it will 'be seen that there is a gap orpocket 76 between the end of slot 62 and the stud which, for example, isshown as 58a. Gap 76 accommodates the solder so that a highly reliableelectrical contact may be made. Thus a large glob of solder put over thewhole assembly is not needed and is, in fact, undesirable since anexcess of solder is likely to drop back into the potentiometer when anelectrical lead from a utilization device is soldered to shank portion74 of terminal 12. Alternatively, the internal end of the terminal maybe spot welded to the conductive stud.

By way of example, studs such as 580 are approximately 0.30 inchdiameter and the terminal slot 62, between legs 60a and 60b ofbifurcated end 60, is approximately 0.035 inch wide. Crimping bore 64may range from 0.030 inch diameter to 0.040 inch diameter while gap 76,between the end of the slot and the stud, may range from 0.005 inch to0.015 inch. Terminals 12 may be readily fabricated from /2 hard brass.

In an alternative form of construction, the bifurcating slot is omittedbut all other features of the terminal remain the same including the useof an epoxy resin. That is, the axially bored end of the terminalcomprises a crimping portion followed by an annular groove and a knurledlength. Once again the combined axial length L of the groove and theknurling is only slightly greater than the wall thickness W of thepotentiometer housing. In this embodiment, the stud conductively securedto the resistive element of the potentiometer is in the form of a wirewhich is inserted into the axial bore of the terminal prior to crimping.The wire may then be either soldered or spot welded into the terminal.As in the previous embodiment, crimping of the forward, axially boredend of the terminal causes the forward Wall of the annular groove to beenlarged. The terminal is thereby captured in the potentiometer Wallbetween the distorted end Wall of the annular groove and the undersideof the flange.

From the foregoing description, it will be seen that connection of theinternal elements of a potentiometer to external terminals has beengreatly simplified without any sacrifice in accuracy or reliability. Thepoints of soldering are fully exposed and accessible so that the smalland delicate components are in no danger of damage. The soldering orwelding may be done to the periphery of the base member on the sideopposite that of the resistive track. The terminal itself is arelatively inexpensive part to fabricate. The method of assemblyrequires no special skills over and above those'of the averageassembler. Knowing the angular position of each stud, it is a simpleprocedure to index the flange portion of the base member to accuratelyalign the radial holes required for the terminals.

A feature of the present invention is that the terminal may bepositioned in the potentiometer wall With the crimped portion eitherinside or outside the housing and the head beyond the flange can takeany convenient shape. Furthermore, the improved terminal permits the useof simple pliers as the crimping tool, it being another feature that asingle tool closes the axial bore of the terminal about the conductivestud and also distorts the terminal so that it cannot be pulled out. Theimproved terminal of the present invention has particular utility in asmall, compact potentiometer wherein conventional flaring tools cannotbe used in the limited space so as to flare over the end of aconventional hollow terminal.

There has been disclosed heretofore the best embodiments of the presentinvention contemplated and it is to be understood that various changesand modifications may be made by those skilled in the art withoutdeparting from the spirit of the invention.

What is claimed is:

1. A one-piece electrical terminal adapted for insertion into anaperture wall, said terminal comprising:

(A) a first deformable tubular section having means to receive anelectrically conductive member therein;

(B) a second substantially nondeformable tubular section having a smallouter diameter than that of said first section, said second sectionextending axially from said first section and being characterized by awall thickness less than that of said first section;

(C) a third section of greater cross sectional dimension than that ofsaid second section and extending axially from said second section todefine a juncture therebetween; and

(D) an enlarged flange portion formed proximate said third section, saidflange portion being disposed in a plane transverse said second andthird sections,

(E) said third section and said second section of said terminal beingdisposed Within the wall aperture in the assembled condition.

2. The terminal according to claim 1 wherein said third section isknurled.

3. The terminal according to claim 1 wherein the axial dimension betweenthe juncture of said first and second sections and said transverse 1ygreater than the thickness of the apertured wall.

4. The terminal according to claim 1 wherein said first section islongitudinally slotted in a diametric plane to define a pair of spacedlegs, the slot being open at one end and closed at the other end.

5. The terminal according to claim 4 wherein the diameter of the axialbore is at least as large as the width of the axially extending slot.

6. A potentiometer comprising:

(A) a housing having an apertured Wall;

(B) a support member mounted within said housing;

(C) a resistance element carried by said support member;

(D) a shaft rotatably journaled in said housing;

(E) takeoff means secured to said shaft for rotation therewith, saidtakeoif means being arranged to slide on said resistance element;

(F) stud means carried by said support member, said stud means being inelectrical connection with said resistance elements; and

(G) one-piece terminal means disposed in the aperture of said housingWall, said terminal means comprising:

(I) a noncircular, first tubular section having flange portion isslightmeans to r e' 'd t d 5.0

cc ive sa1 s u means 1n electrical RICHARD M. WOOD, Primary Examinerconnection therein; (II) a second tubular section having its outerdimensions less than those of said first section, said second sectionextending axially from said first section and being charcterized by aWall thickness less than that of said first section;

(III) a third section of greater cross sectional dimension than that ofsaid second section and extending axially from said second section to todefine a juncture therebetween; and

(IV) an enlarged flange portion formed proximate said third section,said flange portion being disposed on one side of said housing wall in aplane transverse said second and third section,

(a) the major dimension of the noncircular, first tubular section beinggreater than the aperture in said housing wall,

(b) said third section and said second section of said terminal beingdisposed in the wall aperture of said housing in the assembledcondition.

7. The combination in accordance with claim 6 wherein said noncircularfirst tubular section of said terminal is disposed within said housing.

8. The combination in accordance with claim 6 wherein said third sectionis knurled.

9. The combination in accordance with claim 6 wherein the axialdimension between the junction of said first and second sections andsaid transverse flange portion is slightly greater than the thickness ofthe apertured Wall.

10. The combination in accordance with claim 6 wherein said firstsection is longitudinally slotted in a diametric plane to define a pairof spaced legs, the slot being open at one end and closed at the otherend.

11. The combination of claim 8 wherein a cement is disposed in the spacebetween said knurl and the inside surface of the Wall aperture.

12. The combination in accordance with claim 11 wherein said cement isan epoxy resin.

13. The combination of claim 10 wherein the diameter of the axial boreis at least as large as the width of the axially extending slot.

References Cited UNITED STATES PATENTS 1,449,727 3/ 1923 Bowman.

2,464,405 3/ 1949 Knauf.

2,904,767 9/1959 Vacha 338l62 X. 2,909,758 10/1959 Modrey 33922O2,962,691 11/1960 Mande et al 339-276 X 3,093,435 6/1963 Johnson 339-276J. G. SMITH, Assistant Examiner.

1. A ONE-PIECE ELECTRICAL TERMINAL ADAPTED FOR INSERTION INTO ANAPERTURE WALL, SAID TERMINAL COMPRISING: (A) A FIRST DEFORMABLE TUBULARSECTION HAVING MEANS TO RECEIVE AN ELECTRICALLY CONDUCTIVE MEMBERTHEREIN; (B) A SECOND SUBSTANTIALLY NONDEFORMABLE TUBULAR SECTION HAVINGA SMALL OUTER DIAMETER THAN THAT OF SAID FIRST SECTION, SAID SECONDSECTION EXTENDING AXIALLY FROM SAID FIRST AND SECTION AND BEINGCHARACTERIZED BY A WALL THICKNESS LESS THAN THAT OF SAID FIRST SECTION;(C) A THIRD SECTION OF GREATER CROSS SECTIONAL DIMENSION THAN THAT OFSAID SECOND SECTION AND EXTENDING AXIALLY FROM SAID SECOND SECTION TODEFINE A JUNCTURE THEREBETWEEN; AND (D) AN ENLARGED FLANGE PORTIONFORMED PROXIMATE SAID THIRD SECTION, SAID FLANGE PORTION BEING DISPOSEDIN A PLANE TRANSVERSE SAID SECOND AND THIRD SECTIONS, (E) SAID THIRDSECTION AND SAID SECOND SECTION OF SAID TERMINAL BEING DISPOSED WITHINTHE WALL APERTURE IN THE ASSEMBLED CONDITION.